2 a (b^2 - a^2) D[w[a], a]^2 + w[a] ((3 a^2 - b^2) D[w[a], a] + a (a^2 - b^2) D[w[a], {a, 2}]) - a w[a]^2 == 0 /; w[a] == ArithmeticGeometricMean[a, b]

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2001-10-29